It is known that, in accordance with the existing regulations, pumps for fountains may be powered directly using the mains voltage. It is also known that underwater lamps and lighting systems, both for external fountains and for table-top or ornamental fountains, fall within protection class III and must therefore be provided with a transformer which reduces the mains voltage to a maximum safety value of 24 V.
The solutions known from the prior art in this field essentially consist of two different types.
A first type of solution uses a transformer for supplying power in parallel both to the pump which circulates the water in the fountain and to the lighting system. This solution may be advantageously used for low-power pumps and lighting systems. The main drawback of this solution consists in the fact that the transformer must have a size suitable for satisfying the power requirements of both the pumping and the lighting system. When the power required jointly for pumping and lighting increases beyond certain values, the cost of the transformer is such that this solution becomes difficult to realize from a cost point of view.
According to a second type of solution, the pump for circulating the water is powered from the mains voltage, while the lighting system is powered by a separate transformer. This solution is preferred when the power of the pump is such as to require a very large and costly transformer. It is therefore preferred to power only the lighting system with low voltage, using low-power transformers which still have an acceptable cost.
Two examples of embodiment, which belong to this second type of solution, are described in U.S. patent publication Ser. No. 6,196,471 and German patent No. 4337923. In both these examples, a separate transformer is connected to the lighting system and has exclusively the function of lowering the power supply voltage of the lighting system to the safety voltage of 12 V.
The drawback of using a separate transformer for the lighting system consists in the fact that it introduces a complication into the overall system and an additional cost. It is therefore necessary to find a housing of suitable shape and size for the transformer and perform the necessary connections in a safe manner. The number of additional components to be acquired and assembled comprises the transformer, the cables and the safety plugs. Moreover, the risk of components being subject to possible faults increases.
U.S. Pat. No. 4,564,889 describes a solution for powering a lighting system for fountains, swimming pools or domestic showers without using a separate transformer. The pressurized water supplied from a direct line or from a circulating pump is used to actuate a rotor connected to a small alternator. In this way the alternating current necessary for powering one or more lamps is generated.
A drawback of this solution may consist in possible discontinuous operation. In fact, a variation in pressure or throughput of the water which causes rotation of the alternator may cause non-uniform operation of the lighting system and unattractive aesthetic effects.
Further disadvantages consist in the limited lighting power which can be obtained and in the inevitable loss of head downstream of the alternator impeller, which may be troublesome or unacceptable.